Field of the Invention
This invention relates to document transport systems. Such systems are used in machines of many different types for transporting documents along a track, for example for automatic processing of the documents. One particular machine involving the use of a document transport system is a check encoding machine for the automatic processing of bankers' checks.
In check encoding machines, as well as in many other machines using document transport systems, it is desirable to maintain one edge of the document in contact with a reference surface of the track while the document is being moved along the track. One particular transport system includes a drive roller engaging one surface of the document; idler means engaging the opposite surface of the document and resilient means urging the drive roller and the idler means towards each other to grip the document therebetween. In such a system, the axis of rotation of the drive wheel is normally perpendicular to the reference surface and it is known to use an idler roller as the idler means and to arrange the axis of rotation of the idler roller at an angle to the axis of rotation of the drive roller so that the idler roller applies the desired force urging the said edge of the document towards the reference surface of the track. One such system which enables documents to be moved in both directions along the track is described in GB-A-2 171 395. A somewhat similar system is also disclosed in IBM Technical Disclosure Bulletin, Volume 26, No. 7a, December 1983, page 3133.
In another system, the axis of rotation of the drive roller is displaced from the perpendicular to the reference surface so that the drive roller itself applies not only the force required to move the document along the track, but also the force required to urge the document towards the reference surface of the track. In such a system the axis of rotation of the idler roller may be parallel to the axis of rotation of the drive roller, but is preferably capable of being moved from a position in which it is parallel to the axis of the drive roller to a position in which it is perpendicular to the surface reference. In an arrangement in which the axis of the idler roller is movable in this way, the direction of the force applied to the document by the idler roller is also movable so that the force will have a component directed towards the reference surface while the edge of the document is spaced from the reference surface, but this component will be eliminated when the edge of the document comes into contact with the reference surface. Such an arrangement therefore reduces the risk of buckling of the document.
A system of the kind described in the preceding paragraph is relatively complicated and therefore expensive, and it is an object of the present invention to provide a system which has a similar effect to that described, but which is simpler and therefore less expensive.